An Unusual Case of Macrophage Activation Syndrome (MAS)- Hemophagocytic Lymphohistiocytosis (HLH) Triggered by Necrotizing Autoimmune Myopathy.

Macrophage activation syndrome (MAS)- hemophagocytic lymphohistiocytosis (HLH) secondary to inflammatory myopathies such as dermatomyositis (DM), polymyositis (PM), and necrotizing autoimmune myopathy is exceedingly rare in the medical literature. We present the complicated diagnosis and treatment of a 41-year-old female who presented with proximal muscle weakness and shock. Following an extensive critical care workup, she was diagnosed with MAS-HLH, triggered by a newly diagnosed necrotizing autoimmune myopathy. In this case report and literature review, we would like to highlight the importance of recognizing the clinical signs of MAS-HLH in rheumatological disorders and the necessity for rapid treatment.